Thyroid disease: what is it?

Thyroid disease is one of the most common hormonal diseases found in our society today. The most prevalent thyroid gland disorders are hyperthyroidism, hypothyroidism, and thyroid nodules.

Hyperthyroidism means there is too much thyroid hormone, which causes your metabolism to speed up. In many ways it is as if the body is stuck in "overdrive." The heart rate increases, muscles can become weak, and hands can begin to shake with a tremour. Bowel movements can be more frequent, and many people feel a sense of agitation or anxiety.

Hypothyroidism means there is too little thyroid hormone. This lack of thyroid hormone makes most of the body's organs slow down their function. Some people remark that they feel "like an engine that is not running on all cylinders." In many ways the symptoms of an underactive thyroid are opposite to those of an overactive or "hyper" thyroid gland. The heart rate slows, muscles become slow and weak and often ache, bowels become constipated, and people feel less energetic.

A thyroid nodule is an enlarged area or lump of tissue. Thyroid nodules are surprisingly common; how common depends on how hard you look for them. The vast majority of thyroid lumps are benign (not cancerous).

What is the thyroid gland - what does it do?

The thyroid gland is just under the skin in the front of your neck, just below your Adam's apple, and can be felt with your fingers (Figure 1). The thyroid gland is important because it produces thyroid hormones, which are necessary for the normal function of virtually all organs in the body. The 2 most important thyroid hormones are thyroxine (T4) and triiodothyronine (T3). These hormones, along with thyroid stimulating hormone (TSH) can be easily measured by taking a blood sample.

The role of the pituitary gland

The pituitary gland makes TSH and releases it into the bloodstream (Figure 2). TSH travels to the thyroid and causes the thyroid to release the hormones T4 and T3. T4 and T3 then travel through the bloodstream and regulate the function of various organs and metabolic processes within in your body. Some T4 is converted to T3 after leaving the thyroid.

What about iodine?

Iodine, an element found in food and water, is essential for the thyroid gland to produce thyroid hormones. Iodine deficiency is a cause of hypothyroidism, but varies in prevalence depending on geographic regions. For example, in North America and Europe, iodine deficiency is extremely rare because iodine is routinely added to salt. However, for people living in underdeveloped countries this is not the case, so iodine deficiency becomes a threat.

Is thyroid disease hereditary?

If a close relative has either an overactive or an underactive thyroid, then you are at increased risk for developing thyroid disease. Often, one relative will have an overactive thyroid and the next will have an underactive thyroid. This is not something that should be worrisome, however, as most people who have relatives with thyroid disease will not develop thyroid disease themselves. Despite the family history and the resultant increased risk, the vast majority will still not get thyroid disease.

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